Such rings are known and used on a wide scale. Their purpose is to enable a mechanical link to be established between an anchoring device incorporated in the concrete and a hook of a hoist such as crane.
More particularly, the present invention relates to a ring designed to co-operate with an anchoring device having an eye or a tear-out cone associated with a cylindrical head, even though the ring may also be implemented with other anchoring pieces.
When the concrete is being cast, the anchoring piece projects into a void that is hemispherical or partially hemispherical so as to be accessible after unmolding or removal of shuttering.
Such a ring is described in FR-A-1 568 605 and in FR-A-2 302 398 (HAEUSSLER). It comprises a coupling piece or yoke for coupling with the head of the anchoring device and a ring proper or shackle which provides the connection between the coupling piece and the hook of the hoist.
The yoke includes a groove or slot in the form of a circular sector in which the head of the anchoring device is received. In certain known lifting rings, the spherical coupling piece is hinged to the shackle in such a manner as to be capable of pivoting between a position in which the head can be engaged and disengaged in the groove, and a transport or handling position in which the head of the anchoring device is in abutment against the bottom of the groove.
The prefabricated element can thus be transported in complete safety so long as the rated load of the anchor piece corresponds to the weight of the element. After transport, the groove can be moved relative to the head of the anchoring device until the disengagement position is reached.
The top portion of the yoke includes a hinge eye or hole extending orthogonally to the plane of the groove and located eccentrically relative to the center of the hemispherical portion. The hook-receiving shackle is itself engaged in the hole by a circular section arc or rod that enables the parts to be hinged relative to each other. In order to facilitate relative rotation between the yoke and the head of the anchoring device, it is also known to provide said part with a handling tab or arm. The tab may be remotely controlled by means of a cable.
It is necessary to prevent the shackle or coupling part spoiling the surface of the concrete which is still somewhat fresh. That is to avoid subsequent expensive finishing on-site.